The basic objective of this proposal is to determine the cause and the meaning of the accumulation of free proteogenic amino acids which has been found to precede opacification in several types of experimental cataract, and is believed to be an early event in human cataract. A variety of experimental cataracts will be studied and the progression and correlation of changes in free amino acids, other metabolites, hydration, permeability, levels of cations and anions, and protein turnover and content will be studied. Several kinds of nutritonal deficiency will be examined as possible contributory causes of cataract, and a variety of nutritional supplements will be tested for possible effect in the prevention or delay of toxic cataracts. A protocol is being developed for determining as many as possible diferent indicators of lens composition and function on a single lens. It is expected that this will permit improved evaluation of the order of events during experimental cataractogenesis, and it is hoped that such an analytical approach, applied to well-characterized human cataracts, may help to distinguish between different etiologies, and may lead to discovery of methods for prevention or delay of lens opacification.